Profiling of neuraminidase inhibitory polyphenols from the seeds of Paeonia lactiflora.

Bacterial neuraminidase (NA) is a lynch pin enzyme in the formation of biofilms. Thus NA continues to be one of the key enzymes targeted by bacterial infection. The purpose of this manuscript is to communicate four new naturally derived inhibitors of neuraminidase (IC50s 3.7-24.4μM). All these active species (1-4) contained a resveratrol chemotype, however resveratrol itself was inactive (IC50>100μM). 1-4 were isolated from the 60% aqueous ethanol extract of seeds of Paeonia lactiflora, which exhibited potent neuraminidase inhibition. Purification of the extracts yielded four chiral polyphenols, suffruticosol A (1), suffruticosol B (2), trans-ε-viniferin (3), and trans-gnetin H (4). Mechanistic analysis of 1-4's inhibition showed that they were all reversible, noncompetitive inhibitors. Trans-ε-viniferin (3) underwent trans-cis isomerization, which led to a reduction in inhibition potency. This correlates with the fact that the cis-isomer is a weaker inhibitor of neuraminidase than the trans-isomer. Importantly, significantly different optical rotations ([α]D) compared to previous reports were found for suffruticosols A (+95 vs -34) and B (+136 vs +13). These two species are the most important standard metabolites in the whole paeoniaceae family and therefore correction of this error is important.